postgres-fdw docs: `has_permission = true` examples do not work

The Lookup Resources / Lookup Subjects examples in internal/fdw/README.md (and a few in Architecture.md) filter on AND has_permission = true, but running them as documented fails:

ERROR:  unsupported feature or query type: unsupported select statement: operation not supported: column_ref:{...sval:"has_permission"...}

ERROR:  unsupported feature or query type: unsupported select statement: operation not supported: column_ref:{...sval:"has_permission"...}

Postgres folds = true into a bare column reference before pushdown, and the proxy rejects has_permission in WHERE clauses.

Writing the filter as has_permission IS true works through postgres_fdw (it's evaluated locally as a Filter instead of being pushed down), so the README examples should use that. The Architecture.md examples describe SQL as received by the proxy, where no local filtering exists — those should just drop the condition.